@ Raz - get-um while congress is on vacation!
Not a bad deal these days, at Target Sports USA
Federal 5.56mm XM855 NATO 62 Grain FMJ 420 rds on Stripper Clips in Ammo Can
Special $210.00
FREE SHIPPING INCLUDED
My rifle has a slow twist (1:9), so the higher price for the heavier bullet doesn't buy me anything. I stock up when I get the 55gr at around $0.40@. My next such rifle will have a faster twist and a longer barrel.
Just re-barrel it.
But then I don't have an excuse to buy another gun.
But you don't have the money for a new AR anyway so just what difference does it make at this time?
I thought "hunting rifle" was next on the list... not that you couldn't hunt with another AR. Does he already have a .308? 
Oh, and I'm not terribly interested in a .308.
You were not interested in a full size .40 either so you bought two.
I didn't say I wasn't interested in it, only that I didn't NEED it.
I don't need a .308, but I'm also not particularly interested in that cartridge.
A .308 is a fundamental member of every Murican arsenal.
Used to be. It's outdated technology now.
Wonder why they still sell so many of them in modern rifles 
Same reason they still sell so many 1911's in 45acp. Tradition, heritage, aesthetics, and personal preference. A 308 will get the job done, just not something I'm personally exercised about. Personal preference.
And BTW, I can afford whatever I decide is important to me. The 308 just isn't that important to me right now. But that could change tomorrow, just like it did last week for a couple of FNS-40's.
I was waiting on that and sure enough you got it backwards
. The correct answer would be "for the same reason they sell so many Modern Guns in .45 ACP".
I was covering the fact that both the 1911 and the 45acp are dated.
Some mighty modern upgrades to .45 acp ammo, hell I have gone back to carrying .45's almost all the time now - but not 1911's.
Of course. But if bullet technology can keep the bullet together and get it to stop inside the target, then there are advantages to driving a smaller bullet faster - most important of which, you can carry more ammo for weight and the bullets are cheaper. But then there's the eternal debate of how much ammo does one need for self defense? And it'll never be answered.
Fact of the matter is, bullet for bullet it doesn't matter anymore - at least when discussing the use of handguns against two-legged critters.
I embraced 40's for no reason other than I've got multiple friends who will handload for me.